Medical articles are frequently used for delivery of one or more therapeutic agents to patients. For example, an implantable or insertable medical device, such as a stent or catheter, may be provided with a coating layer that contains a polymer and a therapeutic agent. Once the medical device is placed at a desired location within a patient, the therapeutic agent is released from the medical device into the patient, thereby achieving a desired therapeutic outcome.
In general, the formation of such coating layers is simplified where a solvent is available that can effectively dissolve both the therapeutic agent and the polymer of interest. In many instances, however, it is desirable to use water as a solvent, for example, where a preferred therapeutic agent is soluble in water or where solvent toxicity issues may arise. Unfortunately, many polymers that are desirable for the formation of therapeutic-agent-containing regions on medical articles (for example, biostable polymers) are insoluble in water, presenting difficulties in forming release regions. Present formulation techniques for such systems typically involve forming a solution of the polymer of choice in organic solvent and then attempting to disperse the drug in the solution. These techniques commonly require a substantial amount of mechanical agitation to keep the drug from settling out of solution, and can result in unacceptable phase separation in the final product.